1. Field of the Invention
The present invention relates generally to the field of plant breeding. In particular, the invention relates to agronomically elite soybean varieties with commercially significant yield and a mid/low-linolenic acid content.
2. Description of Related Art
Soybean seeds are an important source of vegetable oil, which is used in food products throughout the world. The relatively high level (usually about 8%) of linolenic acid (18:3) in soybean oil reduces its stability and flavor.
Hydrogenation of soybean oil is used to lower the level of linolenic acid (18:3) and improve both stability and flavor of soybean oils (Dutton et al., 1951; Lui and White, 1992). However, hydrogenation results in the production of trans fatty acids, which increases the risk for coronary heart disease when consumed (Hu et al., 1997).
Varieties of low linolenic acid soybean have been produced through mutation, screening and breeding (Fehr et al., 1992; Rahman and Takagi, 1997; Ross et al., 2000; Byrum et al., 1997; Stoisin et al., 1998). Varieties with a linolenic acid content on the order of 1% or lower in particular have been produced (U.S. Pat. Nos. 5,534,425 and 5,714,670). However, the low linolenic acid lines produced to date have been plagued poor seed yield and other agronomic characteristics desired for commercial production. The problem has been difficult to solve and is complicated by the quantitative nature of agronomic traits such as linolenic acid content and yield. The usefulness of low linolenic acid content soybean has therefore been limited in most commercial settings.
Developing a product with commercially significance seed yield is a high priority in most soybean cultivar development programs. Yield is controlled by many genes and strongly influenced by the environment. It is a characteristic of central importance to the commercial value of a variety and breeders continually attempt to improve yield beyond that presently available. It is a difficult challenge to incorporate low linolenic acid content into high yielding cultivars.
Likely because of the difficulty, the prior art has failed to provide high yielding soybean varieties that also posses low linolenic acid and agronomically elite characteristics. However, there is a great need in the art for such soybean plants. The Food and Drug Administration (FDA) has proposed regulations on nutrition labeling to require that the amount of trans fatty acids in a food be included in the Nutrition Facts panel. In addition to the health benefits of reducing our reliance on hydrogenation of soybean oils, the aforementioned proposal by FDA has sparked great interest in the production of low linolenic acid (less than 3%) soybean that does not require, or requires less hydrogenation. Decreased linolenic acid can significantly improve the value of a soybean harvest. For the decreased linolenic acid to have commercial significance, yield and/or elite agronomic traits must not be substantially impacted. Therefore, providing soybean plants that are agronomically elite while both high yielding and possessing decreased linolenic acid would represent a substantial advance in the art and benefit farmers and consumers alike.